"It's going to happen," said Dr. Greg Poland of the Mayo Clinic. "For the American public in particular, I think it will be horrific."
Many Americans haven't experienced the overwhelming crush of patients at hospitals and doctors' offices and the widespread fear a flu pandemic could bring. And by historical pattern, Poland said it's about time for the next one.
There have been three in the past 100 years, igniting in 1918, 1957 and 1968. There's no way to predict when the next one will appear, but the pattern does give experts pause.
It's all up to a virus that is variable and fickle, constantly changing its genetic makeup, and the time when it hits upon a combination that lets it take off worldwide is a "roll of the genetic dice," said Dr. William Schaffner of Vanderbilt University.
So the lack of a pandemic in the past 35 years basically means "the genetic dice haven't been rolled that way," Schaffner said. "While we're grateful for that, it makes us nervous."
There's plenty to be nervous about. It's estimated that in the industrialized nations alone, the next pandemic is likely to send 1 million to 2.3 million people to the hospital and kill 280,000 to 650,000, according to the World Health Organization. Its impact will probably be greatest in developing countries.
As a practical matter, flu shots probably could not be counted on to prevent a pandemic. For one thing, pandemic virus strains emerge unexpectedly, and there would probably not be enough time to recognize the threat and then provide vaccines that target them, Schaffner said. What's more, many countries outside the United States wouldn't have the means to give enough flu shots to stop the spread, Poland said.
To cope with the current outbreak, the federal government is scrambling to ship 100,000 adult vaccine doses to combat shortages, hoping to head off what could become one of the worst flu outbreaks in years, and 150,000 child vaccines are expected in January.
The Department of Health and Human Services said the adult doses should be ready for distribution this weekend to state health departments, based on population.
The government bought the doses from manufacturer Aventis Pasteur, and H.H.S. Secretary Tommy Thompson says other possibilities are being explored.
Meantime, people have been lining up across the nation, trying to find what has become an ever-more-elusive prize. Many states and cities are holding their dwindling supplies for people most at risk of developing complications, the elderly and the very young.
Some hospitals were discouraging visitors after officials announced the flu had spread to all 50 states.
The number of states with widespread infections nearly doubled to 24 in the past week, and the season has not yet peaked nationally, the CDC said Thursday.
Many schools have shut down. Emergency rooms have been filled with sick children. And doctors' offices have been forced to turn away droves of people seeking flu shots.
Health officials are unsure why the outbreak has hit so early, why it has caused so many problems and why it seems to be so hard on children.
States are not required to track the number of flu cases, so the exact total is not clear; however, at least 20 children have died nationwide during this outbreak.
Despite the severity of the early outbreak, health experts are not ready to predict just how bad the flu season will be. The season still may peak as early as December, rather than February, which is the norm.
The nation's two producers of flu shots reported last week that they had shipped their entire supply of about 80 million doses. However, Aventis Pasteur had set aside 250,000 doses at the CDC's request last week when it became clear that shortages might develop. Those are the doses being shipped now.
Manufacturers of tests used to determine if a patient has the flu say the current outbreak has strained their ability to meet demand from hospitals, medical laboratories and doctors' offices.
Also, drug stores and online companies around the country are reporting brisk sales of both over-the-counter remedies and prescription drugs in the past few weeks.
Among prescription drugs, demand has picked up for Tamiflu - which can prevent or relieve the flu - and for FluMist, a nasal version of the flu vaccine, according to the makers of the medicines. They gave no numbers.
Some stores have reported intermittent shortages of certain products.
Several insurance companies in New Jersey said they will cover costs for a new nasal flu vaccine during this flu season, according to a report.
AmeriHealth, Aetna, Oxford Health Plans and Horizon have made, or are making, arrangements to cover the vaccine, a nostril spray called FluMist. They cited a shortage of flu shots and early incidents of flu outbreaks around the country.
Most companies said they would return to their normal policies after this flu season ends in the spring.
Many Americans living along the U-S and Mexican border were traveling to Mexico to buy flu shots after their cities ran out.
Mexican pharmacies don't require prescriptions, and at least one pharmacist in the border city of Tijuana reported a jump in sales of 500 percent.
As for the possible pandemic, Dr. Robert Couch of the Baylor College of Medicine noted that health authorities are making major efforts to prepare for 익산출장마사지
controlling one, including putting an emphasis on developing and manufacturing vaccines faster and in greater quantities.
The pandemic of 1918-19, known as the Spanish flu, sickened an estimated 20 percent to 40 percent of the worldwide population, with a death toll believed to exceed 20 million. In the United States alone, some 500,000 people died. In the United States, an ordinary flu epidemic kills an average of 36,000 people.
The next pandemic, the Asian flu of 1957-58, killed about 70,000 in the United States, while the 1968-69 Hong Kong flu led to about 34,000 deaths in the United States.
New strains of the flu virus, and so potential pandemics, get their start in rural Asia, where the various strains that infect chickens and other birds, pigs and humans can mingle. That gives them a chance to swap genetic information as well as mutate on their own.
The potential spark for a pandemic occurs when that environment produces a new virus that infects people and bears surface proteins that people's bodies have never seen before. That means people have no natural defense against it.
In contrast, ordinary outbreaks like this year's come from a virus that has changed only slightly from previous ones, so that the population it enters still has some natural immunity
from encounters with the previous germs.
But the genetic shift alone is not enough to launch a pandemic. In addition, the new virus must acquire the ability to pass easily from person to person, either by random genetic change or by picking up genetic material from a previous human flu virus.
The world has had some close calls in the past few years, says Richard Webby of St. Jude's Children's Research Hospital in Memphis. In 1997, a bird flu in Hong Kong jumped to people, killing six. But the virus never developed the ability to pass easily from person to person, Webby said. Hong Kong authorities slaughtered 1.4 million chickens to end the threat.
Just this year, authorities became alarmed when a father and son in Hong Kong were hospitalized because of a bird flu virus, and when flu virus infected some workers in the Netherlands who had slaughtered infected chickens.